This invention relates generally to the field of vehicle steering control, and in particular, to a system and method for digital steering sensor fault detection.
With the increase in electronic monitoring and control in vehicles, there is a need for information on steering wheel position for multiple vehicle control modules such as suspension ride control. Currently, sensors having both analog and digital outputs are used.
Considerable reduction in both sensor and controller costs can be realized by omitting the hardware associated with the analog signal. Digital signals are more forgiving than analog signals when shared. Ground offsets, ratiometric outputs, impedance loading and etc. do not impact digital signals as they do for analog signals. However, diagnosing signal and sensor faults are very difficult for a controller receiving digital signals alone.
Presently, if a digital handwheel position sensor does not see vehicle handwheel rotation, as occurs if the vehicle is driven straight, the signals stay constant (either high or low). Therefore, the sensor""s output for a vehicle driven straight has the same exact signal characteristics as a failed sensor or output. Because of this situation, digital handwheel position sensors typically incorporate an analog signal output to diagnose sensor faults. Typical diagnostic requirements are to detect the following faults/conditions: 1) digital output signal open circuited, shorted-to-battery or shorted-to-ground; 2) digital steering sensor ground (return) circuit open; and 3) digital steering sensor supply circuit open. A controller module receiving only digital steering signals has no means of determining that a digital handwheel position sensor or one of its outputs have failed.
Accordingly, it would be desirable to have a system and method for digital steering sensor fault detection that overcomes the disadvantages described.
One aspect of the invention provides a system and method for digital steering sensor fault detection that avoids the need for steering sensor analog outputs.
Another aspect of the invention provides a system and method for digital steering sensor fault detection that is able to discriminate between sensor faults and normal operation.
Another aspect of the invention provides a system and method for digital steering sensor fault detection that is able to detect faults and conditions, such as: 1) digital output signal open circuited, shorted-to-battery or shorted-to-ground; 2) digital steering sensor ground circuit open; and 3) digital steering sensor supply circuit open.
The invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.